Manufacture of waterproof fibrous products



, 30 articles such as mi Patented Feb. 24, 1931 UNITED STATES manner 1.. cmrr, or nnwnas, ussacnusms MANUFACTURE OF WATERPROOF FIZBBOUS PRODUCTS 1\o Drawing.

In manufacturing fibrous products, such as those made from cellulose pulp, it has heretofore sometimes been the custom to waterproof the pulp fibers in the beater engine b adding suitable sizing materials and precipitating such materials on the fibers before forming into the desired product and drying. When pulp so sized is used as a raw material in making moulded pulp articles,

. as for instance by introducing the pulp mto foraminous moulds, then dewatering by forcing the pulp against the moulds by air, preferabl in heated condition, under pressure, and nally removing thearticles and drying,

. it has been found that considerable sizing material may be forced through the moulds along with the water of the pulp suspension,

* and is lost. In actual practice, it has been found uneconomical to incorporate more than about 5% sizing material in the fpulp,

since sizing material usedg'in excess 0 this A amount is apparently lost and tends to plug the moulds. This limited amount of sizing material, however, does-not result in articles which are thoroughly waterproof, so that bottles require a special after-treatment with waterproof material,

' such as spra with parafiin wax onthe inside. Not only is such after-treatment exnsive, but at best is a makeshift cure, since 1t is difiicult to waterproof uniformly the inside of articles such asbottles.

I have discovered that a uniform suspension of pulp and molten thermoplastic waterproofing material, such as parafiin, may be prepared, if such molten material is agitated into a ulp suspension heated above the melting point of such material, and that such a heated mixed su nsion may be made into fibrous products, or instance moulded fibrous articles, which are highly waterproof.

The molten waterproofing material tends to coat the individua fibers, any excess remain-. ing suspended in ules which permeate the fibrous product, filling the pores and interstices thereof. For

the form of discrete glob:

Application filed September 27, 1928. Serial No. 308,880.

instance, when the mixed suspension is introduced into foraminous moulds, the resulting-article is highly waterproof, not only because the individual fibers are encased in waterproofing material but also because the discre globules fill the pores and interstices of the article as the water in which they are suspended passes throughthe fibrous material and out of the mould. In order to avoid separation of the waterproofing material from the suspension, it is necessary that the suspension be maintained in agitated condition above the melting point of suchmaterial. Along with the waterproofing material, precipitable sizing material,. such as rosin size, may be added to the pulp, a suitable precipitant such as alum then being added to fix the sizing on the pulp fibers. The precipitate thus produced ensures a better and more uniform retention of molten waterproofing material on the fibers, as it tends to carry down and fix the suspended 'particles ofunolten material on the fibers. The process of the present invention further permits of the successful use of certain cel- 7 lulose pulps which Were heretofore found unsatisfactory. Thus, 'in the moulding of articles, it has heretofore been necessary to use a free pulp, such as ground-wood pulp, since water may be removed quickly from such pulp, and the moulded article is of sufiieiently low water content to be handled. By moulding a heated pulp suspension as herein described,slowness is avoided even in the case of pulps such as kraft and sulphite, 35 so that articles of higher strength maybe successfully moulded therefrom, owing to the greater fiber length of such pulps. Articles such as milk bottles, when made as herein, described, are practically sterile, bacteria and bacteria culture present in the pulp apparently having'been destroyed by the elevated temperaturetreatment, which may 1 extend over a comparatively long period of time. This is an important feature of the present invention, as heretofore pulp articles of the character described have been shown to contain a com a'ratively high bacteria content. Various t ermoplastic waterproofmo ingmaterials maybeusedincarryingout present invention may by giving specific exof kraft pulp may be introduced into a beater engine, together-with sufficient water to permit circulation and the proper beating out or disintegration of the pulp, and the beater roll set in operation. The Water used may be at elevated temperature, or else steam may beinjected directly into the stock during beating, the pulp thus being conditioned at a temperature of, say, 150 to 190 F., withoutbeing-gelatiniz'ed or slowed down materially. Into the hot stock being beaten is then poured slowly 150 pounds of paraflin, or mixture of pounds of paraffin and 50 pounds of unsaponifiedrosin at 190 F., the molten thermoplastic material being of suili-- ciently low viscosity at this temperature to be uniformly disseminated throughout the stock quite readily during the operation of the beater. The uniform suspension of pulp fiber and molten thermoplastic material, after beating for, say, about two to three hours at a temperature above the melting point of the thermoplastic material, may then be sheeted or it may be introduced into moulds in such hot condition. The hot pulp suspension may be advantageously moulded into articles such as milk bottles, dishes, and toys, as by the so-called Drake process, the suspension supply being maintained in hot condition while portions are being withdrawn and introduced into foraminous moulds faced with wire screening, heated air under pressure then being allowed to enter the moulds to press the pulp against the screening and partially dry the articles, whereupon the ar- 1 tieles are removed from the moulds and drying completed. It is found that the articles may be removed from the moulds with less tendency to sticking and in much drier condition than was heretofore possible.

An importantadvantage of the process of the present invention is that it permits of the re-use of waste produced during manufacturing operations, as raw material. Thus, when articles such as milk bottles, waterproofed with paraflim, are being produced, imperfectly formed bottles or ones damaged by handling may be returned to the beater engine and treated'along with the fresh raw material, the paralfined fibrous material being readily disintegrated into its constituent fibers at a temperature above the melting point of the para Having thus described certain embodisuch as the following:.

pulp and 100 to 200 parts ,lose pulp Waterproofing material, WlllCll comprises inents of this invention, it should be evident to those skilled in the art that various changes and modifications might be made therein without departing from the spirit or scope of invention as defined by the appended claims.

I claim 1. A process of making waterproof fibrous products having thermoplastic Waterproofing material, which comprises mixing such material and a pulp suspension at a temperature above the melting point of such material, and forming the product from the suspension in such hot condition.

process of making waterproof fibrous products having thermoplastic waterproofing material, which comprises heating a pulp suspension above the melting point of such material, mixing such material while in molten condition into the suspension, and forming the product from the suspension in such hot condition.

3. A process of making waterproof celluproducts having thermoplastic beating a. pulp suspension at a temperature above the melting point of such material, adding the material in molten condition to the suspension being beaten, and forming the product from the suspension in such hot condition.

4. A process of making waterproof fibrous products having thermoplastic waterproofing material, which comprises mixing such material and a pulp suspension at a temperature above the meltin point of such material, adding precipitable sizing material, precipitating such material on the pulp fibers, and forming the product from the suspension in such hot condition.

5. A process of making waterproof pulp articles having thermoplastic waterproofing material, which comprises beating a pulp suspension at a temperature above the melting point of such material, adding the material while in molten condition to the suspension being beaten, moulding the suspension in such hot'condition into articles, and drying the articles.

6. A process of making waterproof pulp articles having thermoplastic waterproofing material, which comprises beating a pulp suspension at a temperature above the melting point of such material, adding the material in molten condition to the suspension being beaten, moulding the suspension in such hot condition into. articles, subjecting the wet moulded pulp to air pressure at elevated temperature to remove excess water, and drying.

7. A process which comprises heating a 'pulp suspension to a temperature of about moulding the suspension in such hot condition into articles. Y 8, A process of making waterproof fibrous Eroducts, which com rises disintegrating brous stock associate with thermoplastic waterproofing material above the melting point of such material, and forming the product from'the resulting suspension in such hot condition. m In testimony whereof I have afiixed my signature. I

ALBERT L. CLAPP. 

